[0001] The invention relates to a contactless ignition system of a supply voltage variation
compensation type for an internal combustion engine, particularly an internal combustion
engine for automotive vehicles.
[0002] With known contactless ignition systems of the type in which the length of time a
primary current flows through the ignition coil of an automobile internal combustion
engine is varied in accordance with the engine speed, it is well known to vary a duration
time of the primary current flow through the ignition coil in accordance with variation
of the power supply voltage such that the duration time of the primary current flow
is varied in accordance with an increase or decrease of the power supply voltage from
a predetermined value.
[0003] As an example of this type of systems, a contactless ignition system for automotive
vehicle engines is known (2244 Research Disclosure May 1980, No. 193) which comprises
an AC-generator, a shaper circuit, a driving circuit, a power transistor, an ignition
coil and a storage battery, wherein the energizing interval of time, i.e. the so-called
dwell time, of the ignition coil is controlled in response to both the AC output signal
of the AC generator and the voltage across the battery.
[0004] For this purpose an input transistor is connected to the AC generator to be rendered
conductive and non-conductive in response to the positive and negative half waves
of the AC output signal and an inverting transistor is connected to the power transistor
by means of the driving circuit to render the power transistor conductive and non-conductive
in response to the respective conduction and non-conduction of the input transistor.
The base and collector of the inverting transistor are connected to the positive terminal
of the battery through respective resistors while its emitter is connected to the
negative terminal of the battery through an emitter resistor common with the input
transistor. By this arrangement the base current and the collector current of the
inverting transistor are increased with the increase in the battery voltage, so that
the voltage across the emitter resistor is increased. As a result the switching point
in the AC output signal at which the input transistor changes from non-conduction
to conduction is simply increased, and by this increase the conduction point of the
power transistor is delayed. Thus the dwell time of the ignition coil energized during
the conduction of the power transistor is decreased with the increase in the battery
voltage. However, there is the danger of the input transistor adapted to be turned
on and off in response to the ignition signal being operated erroneously by noise,
temperature changes etc.
[0005] Further an ignition system comprising a Hall effect electronic ignition controller
is known (US-A 4128091), wherein a Darlington output transistor is provided with several
circuit protection networks, among which one network comprises two resistors and a
Zener diode. This protection circuit is provided to protect the output transistor
from the damaging effect of high induced voltages that may appear at the collector
of this transistor under no-load ignition coil conditions when the output transistor
is not conducting. The Zener diode is connected between a divider junction of the
two resistors and the base of the output transistor. Should the voltage at the collector
of the output transistor rise above the voltage rating of the Zener diode as it may
do during no-load or unconnected ignition coil secondary conditions, the Zener diode
breaks down to conduct current into the base of the output transistor to turn it on
slightly and limit the rise of the voltage at its collector output. While the Zener
diode in tthe output circuit is adapted to protect the output transistor variations
of the supply voltage for the input circuit are not compensated.
[0006] In a further attempt to overcome these deficiencies, a supply-voltage-compensated
contactless ignition system for an internal combustion engine has already been proposed,
said system comprising a high voltage generating ignition coil, switch means for controlling
the flow of current from a DC power source to the ignition coil and control means
for controlling the switch means in response to synchronising signals generated by
a signal generator in synchronism with the rotation of the engine, including a compensation
circuit for changing an operating level of an input transistor in response to change
of the DC voltage of said power source, said compensation circuit including a current
mirror circuit for changing said operating level at a first rate of change with change
of said DC voltage not larger than a predetermined value and changing said operating
level at a second rate of change larger than said first rate of change with change
of said DC voltage not smaller than said predetermined value. Thus this ignition system
is designed so that when the supply voltage varies, the operating level of an input
transistor with respect to the ignition signal is not varied linearly but the rate
of change of the operating level is increased in response to the rise of the supply
voltage beyond,a a predetermined value. However, for this purpose an additional compensation
circuit comprising a current mirror circuit has to be provided.
[0007] It is therefore the object of the invention to provide an internal combustion engine
contactless ignition system of the supply voltage variation compensation type which
overcomes the foregoing deficiencies of the prior art ignition systems.
[0008] According to the invention a contactless ignition system of a supply voltage variation
compensation type for an internal combustion engine, comprising an alternator for
generating an alternating current signal in synchronism with the rotation of the engine,
an ignition coil for generating a high voltage, a power transistor for on-off controlling
the primary current of said ignition coil, and input transistor being operated responsive
to said alternating current signal, and an inverting transistor for controlling said
power transistor wherein said inverting transistor having a base connected to a collector
of said input transistor, an emitter connected to one terminal of a power source through
a common emitter resistor with said input transistor having an emitter also connected
to said one terminal of said power source through said common emitter resistor, and
said inverting transistor having a collector connected through a collector resistor
to the other terminal of said power source, is characterized in that a series circuit
of a resistor and a Zener diode is connected in parallel with said collector resistor
and between said collector of said inverting transistor and said other terminal of
said power source, whereby an increase in the power voltage of said power source exceeding
a predetermined value turns on said Zener diode to cause a current flow, when said
inverting transistor is turned on, from said power source to said common emitter resistor
through said collector resistor, said series circuit and said turned-on inverting
transistor, so that the operational level of said input transistor is shifted in dependence
upon said increase in the power voltage in such that said input transistor turns on
and off at different levels of said alternating current signal owing to increase and
decrease in said current flow to said common emitter resistor caused in response to
the turning on and off of said inverting transistor.
[0009] In accordance with the invention there is thus provided a contactless ignition system
having a hysteresis characteristic such that the operating level at which the input
transistor is switched from the off-state to the on-state differs substantially from
that at which the input transistor is switched from the on-state to the off-state,
by which the range of variations in the operating level of the input transistor in
response to variations of the power supply voltage can be increased and thus variations
of the power supply voltage can be compensated in order to avoid an unstable control
by erroneous turning on and off of the input transistor due to noise, temperature
changes, variations in characteristics among mass produced elements and so on.
[0010] Embodiments of the invention are described below with reference to the accompanying
drawings, in which:
Fig. 1 is a circuit diagram showing an embodiment of an ignition system according
to the invention;
Fig. 2 shows a plurality of waveforms illustrating the operation of the input transistor
and useful for explaining the operation of the ignition system shown in Fig 1; and
Figs. 3 and 4 are characteristic diagrams of the ignition system shown in Fig. 1.
[0011] Referring now to Fig. 1 illustrating an embodiment of the invention, numeral 1 designates
an alternator for generating an ac voltage synchronized with the rotation of an internal
combustion engine and the generated voltage generally has a waveform as shown in (A)
of Fig. 2 and increases with an increase in the engine speed from the waveform a to
the waveform b as shown in (A) of Fig. 2. An input transistor 4 and an inverting transistor
5 convert the generated voltage of the alternator 1 to a rectangular waveform which
in turn is subjected to current amplification by transistors 6 and 7 to drive a power
transistor 8. Numeral 2 designates a power source, 3 an ignition coil, 3a an ignition
coil primary winding, 3b an ignition coil secondary winding, 19 a collector resistor
of the input transistor 4, and 20 a collector resistor of the inverting transistor
5 with which a series circuit of a Zener diode 11 and a resistor 23 is connected in
parallel. Numeral 21 designates an emitter resistor for connecting the emitters of
the input transistor 4 and the inverting transistor 5 to the ground side of the power
source 2. When the ac voltage generated by the alternator 1 is converted to a rectangular
waveform by the input transistor 4 and the inverting transistor 5, the operating level
of the input transistor 4 is dependent on the potential at the junction between a
resistor 17 and a diode 10 and the potential at the junction between the transistors
4 and 5 and the emitter resistor 21. The input transistor 4 and the inverting transistor
5 are alternately turned on and off so that when the power supply voltage V
B is low and the Zener diode 11 is off, the operating level for turning on the input
transistor 4 is dependent on the base and collector currents of the inverting transistor
5 which flow respectively through the resistors 19 and 20. On the other hand, when
the power supply voltage V
B exceeds the breakdown voltage of the Zener diode 11, the operating level for turning
on the input transistor 4 rises rapidly in dependence on the base current of the inverting
transistor 5 and its collector current that flows through the parallel connection
of the resistors 20 and 23 and the operating level for turning off the input transistor
4 decreases with a decrease in the current flowing through the emitter resistor 21
due to the turning off of the inverting transistor 5. As a result, the "ON" and "OFF"
operating level of the input transistor 4 forming a part of a waveform reshaping circuit
is provided with a hysteresis effect and this has the effect of preventing any erroneous
operation due to .noise. When the power supply voltage increases beyond the Zener
voltage, the "ON" operating level increases considerably with the resulting increase
in the hysteresis effect. The operation of the embodiment will now be described further
with reference to Fig. showing the relationship between the alternator ac voltage
waveform and the operating waveforms of the input transistor 4 in the construction
according to the invention. In Fig. 2, (A) shows the signal waveform generated by
the alternator 1, with a showing the waveform generated at low engine speed operation
and b showing the waveform generated at high engine speed operation. (B) and (C) respectively
show the on and off operations of the input transistor 4 corresponding to the waveforms
a and b when the power supply voltage is low, and (D) and (E) respectively show the
on and off operations of the input transistor 4 corresponding to the waveforms a and
b when the power supply voltage is high.
[0012] The operation of the ignition system shown in Fig. 1 will be described first with
reference to a case where the power supply voltage V
B is low so that the Zener diode 11 is not turned on. The waveform generated by the
alternator 1 is shown in (A) of Fig. 2. If the operating level V
T of the input transistor 4 is V
T,, in response to the waveform a in (A) of Fig 2, the input transistor 4 is turned
on at a point T
1 in (B) of Fig. 2 so that the inverting transistor 5 is turned off, the transistor
6 is turned on, the transistor 7 is turned off and the power transistor 8 is turned
on. Then, the input transistor 4 is turned off at a point To in (B) of Fig. 2 so that
the power transistor 8 is turned off through the operation reverse to that mentioned
previously. When the speed of the alternator 1 increases so that its output waveform
increases from a to b as shown in (A) of Fig. 2, the slope of the waveform becomes
more sharp and the time at which the input transistor 4 is turned on is shifted from
the point T
1 in (B) of Fig. 2 to a point T
2 in (C) of Fig. 2. In this way, the turn-on point of the input transistor 4 is shifted
to increase the ratio of the ON period (hereinafter referred to as a dwell angle)
of the power transistor 8.
[0013] On the other hand, when the power supply voltage V
B increases and exceeds the breakdown voltage of the Zener diode 11, the current flowing
in the collector resistor 19 of the input transistor 4 and the base and collector
currents of the inverting transistor 5 are increased. Thus, the emitter voltage of
the input transistor 4 rises and its operating level is shifted from V
T1 to V
T2. As a result, at low engine speeds the turn-on point of the input transistor 4 is
shifted from the point T
1 in (B) of Fig. 2 to a point T
3 in (D) of Fig. 2 with increase in the power supply voltage V
µ. At high engine speeds the same turn-on point is shifted similarly from the point
T
2 in (C) of Fig. 2 to a point T
4 in (E) of Fig. 2. In this way, the dwell angle decreases with increase in the power
supply voltage V
µ.
[0014] On the contrary, when the power supply voltage V
B decreases, the operating level of the input transistor 4 is shifted to the lower
value so that the dwell angle is increased and the energization period of the primary
winding 3a is increased (the previously mentioned change from To-T
1 to To-T
2), thus preventing any deterioration in the sparking performance of the ignition coil
3. In Fig. -3, the abscissa represents the engine speed N and the ordinate represents
the dwell angle (8) during which the primary current flows in the ignition coil 3.
In the Figure, e shows an exemplary characteristic of a prior art ignition system,
and f and g respectively show a characteristic of the ignition system of Fig. 1 when
the power supply voltage is low and a characteristic of the same ignition system when
the power supply voltage is high. In accordance with the invention, when the power
supply voltage increases, the dwell angle is decreased so as to limit the current
flowing in the primary winding 3a and thereby to improve the operating reliability
of the power transistor 8. Fig. 4 is a characteristic diagram showing the relation
between the variation of the power supply voltage V
B and the variation of the operating level of the input transistor 4 in the ignition
system of Fig. 1. In the Figure, p shows a characteristic obtained when the power
transistor 8 (the primary current of the ignition coil 3) is switched from the OFF
state to the ON state and q shows a characteristic obtained when the power transistor
8 is switched from the ON state to the OFF state. It will be seen from the Figure
that when the power supply voltage exceeds a predetermined value, the difference between
the characteristics p and q is increased and the hysteresis effect is increased.
[0015] It will thus be seen from the foregoing that there is provided a contactless ignition
system wherein the base of the inverting transistor 5 is connected to the collector
of the input transistor 4 which is turned on and off in response to the generated
output of the alternator 1 for detecting the speed of the internal combustion engine,
wherein the emitters of these transistors are connected through the common emitter
resistor 21 to the negative terminal side of the power source 2, wherein the base
resistor 19 is connected between the base of the inverting transistor 5 and the positive
terminal of the power source 2 to vary the base current of the inverting transistor
5 in response to variation of the power supply voltage, wherein the collector resistor
20 and the series circuit of the Zener diode 11 and the resistor 23 are connected
in parallel with each other between the collector of the inverting transistor 5 and
the positive terminal of the power source 2 so as to vary the collector current of
the inverting transistor 5 in response to variation of the power supply voltage, and
wherein the power transistor 8 is connected to the primary winding 30 of the ignition
coil 3 so as to be turned on and off in the same phase with the input transistor 4
in response to the turning on and off of the inverting transistor 5.
[0016] In accordance with the above-described embodiment, by virtue of the operation of
the Zener diode 11, when the power supply voltage is lower than a predetermined value,
the operating level of the input transistor 4 is reduced to a value close to zero
so that the input transistor 4 is operable even when the output voltage of the alternator
1 is low as during the starting period of the engine. On the other hand, when the
power supply voltage is higher than the predetermined value, the operating level of
the input transistor 4 is shifted to a higher value and thus the time during which
the input transistor 4 is turned on or the time during which the power transistor
8 is turned on (the energization period of the ignition coil 3) is prevented from
becoming excessively large.
[0017] In accordance with the above-described embodiment, by virtue of the fact that the
base current of the inverting transistor 5 is varied in dependence on the power supply
voltage, not only the collector current of the inverting transistor 5 is varied but
also the current which is dependent on the power supply voltage is supplied to the
collector itself of the inverting transistor 5, thus causing the voltage. drop across
the emitter resistor 21 of the input transistor 4 to vary greatly in response to variation
of the power supply voltage. Also, by virtue of the parallel connection of the collector
resistor 20 of the inverting transistor 5 and the Zener diode 11, the voltage drop
across the emitter resistor 21 is maintained at a low value close to zero when the
power supply voltage is lower than a predetermined value and in response to the power
supply voltage higher than the predetermined value the Zener diode 11 is turned on
to greatly increase the voltage drop, thus causing the threshold voltage for turning
the input transistor 4 on to vary greatly in response to variation of the power supply
voltage. Thus, in accordance with the invention, the length of time the primary current
flows is varied so as to effectively follow up the voltage variation in either of
two regions where the power supply voltage is higher and lower, respectively, than
a predetermined value and moreover the length of primary current flow time can be
decreased greatly in response to a variation of the power supply voltage beyond the
predetermined value. Since the operating level shift of the input transistor 4 in
fact shifts only its operating level from the OFF state to the ON state, when the
power supply voltage is high, due to the connection of the Zener diode 11 to the inverting
transistor 5, the difference between the operating level for switching the input transistor
4 from the OFF state to the ON state and that for switching the input transistor 4
from the ON state to the OFF state or the hysteresis is increased, thus preventing
any erroneous operation due to external noise and thereby ensuring stable ignition
operation.
1. A contactless ignition system of a supply voltage variation compensation type for
an internal combustion engine, comprising:
an alternator (1) for generating an alternating current signal in synchronism with
the rotation of the engine;
an ignition coil (3) for generating a high voltage;
a power transistor (8) for on-off controlling the primary current of said ignition
coil;
an input transistor (4) being operated responsive to said alternating current signal;
and
an inverting transistor (5) for controlling said power transistor (8) wherein said
inverting transistor (5) having a base connected to a collector of said input transistor
(4), an emitter connected to one terminal of a power source (2) through a common emitter
resistor (21) with said input transistor (4) having an emitter also connected to said
one terminal of said power source (2) through said common emitter resistor (21), and
said inverting transistor (5) having a collector connected through a collector resistor
(20) to the other terminal of said power source (2);
characterized in that a series circuit of a resistor (23) and a zener diode (11) is
connected in parallel with said collector resistor (20) and between said collector
of said inverting transistor (5) and said other terminal of said power source (2),
whereby an increase in the power voltage of said power source (2) exceeding a predetermined
value turns on said zener diode (11) to cause a current flow, when said inverting
transistor (5) is turned on, from said power source (2) to said common emitter resistor
(21) through said collector resistor (20), said series circuit (23,11) and said turned-on
inverting transistor (5), so that the operational level of said input transistor (4)
is shifted in dependence upon said increase in the power voltage in such that said
input transistor (4) turns on and off at different levels of said alternating current
signal owing to increase and decrease in said current flow to said common emitter
resistor (21) caused in response to the turning on and off of said inverting transistor
(5).
2. A contactless ignition system according to claim 1, characterized in that said
zener diode (11) operates to increase a dwell angle through which said power transistor
(8) is switched on when said power voltage is lower than said predetermined value,
and to decrease the dwell angle when said power voltage is higher than said predetermined
value.
1. Kontaktloses Zündsystem für Brennskraftmaschinen mit Ausgleich der Änderungen der
Spannungsversorgung mit
einem Wechselstromerzeuger (1), der sychron zur Drehung der Maschine ein Wechselstromsignal
erzeugt;
einer Zündspule (3) zur Erzeugung einer Hochspannung;
einem Leistungstransistor (8) zur Ein-AusSteuerung des Primärstroms der Zündspule;
einem Eingangstransistor (4), der auf- das Wechselstromsignal anspricht; und
einem invertierenden Transistor (5) zur Steuerung des Leistungstransistors (8), der
eine Basis, die mit einem Kollektor des Eingangstransistors (4) verbunden ist, einen
Emitter, der über einen gemeinsamen Emitterwiderstand (21) mit einem Anschluß einer
Stromquelle (2) verbunden ist, wobei der Eingangstransistor (4) einen Emitter aufweist,
der ebenfalls über den gemeinsamen Emitterwiderstand (21) mit dem einen Anschluß der
Stromquelle (2) verbunden ist, und einen Kollektor aufweist, der über einen Kollektorwiderstand
(20) mit dem anderen Anschluß der Stromquelle (2) verbunden ist, dadurch gekennzeichnet,
daß eine Reihenschaltung eines Widerstandes (23) und einer Zenerdiode (11) parallel
zu dem Kollektorwiderstand (20) und zwischen den Kollektor des invertierenden Transistors
(5) und den anderen Anschluß der Stromquelle (2) geschaltet ist, wobei ein Anstieg
der Spannung der Stromquelle (2) über einen vorbestimmten Wert hinaus die Zenerdiode
(11) einschaltet, wodurch ein Stromfluß von der Stromquelle (2) über den Kollektorwiderstand
(20), die Reihenschaltung (23, 11) und.den eingeschalteten invertierenden Transistor
(5) zu dem gemeinsamen Emitterwiderstand (21) hervorgerufen wird, wenn der invertierende
Transistor (5) eingeschaltet ist, so daß der Arbeitspegel des Eingangstransistors
(4) in Abhängigkeit von dem Anstieg der Leistungsspannung so verschoben wird, daß
der Eingangstransistor (4) bei verschiedenen Pegeln des Wechselstromsignals infolge
des Anstiegs und Abfalls des Stromflusses zu dem gemeinsamen Emitterwiderstand (21),
der auf das Ein- und Ausschalten des invertierenden Transistors (5) hin hervorgerufen
wird, ein- und ausschaltet.
2. Kontaktloses Zündsystem nach Anspruch 1, dadurch gekennzeichnet, daß die Zenerdiode
(11) eine Vergrößerung des Schließwinkels bewirkt, wodurch der Leistungstransistor
(8) eingeschaltet wird, wenn die Spannung den vorbestimmten Wert unterschreitet, und
eine Verringerung des Schließwinkels bewirkt, wenn die Spannung den vorbestimmten
Wert übersteigt.
1. Un système d'allumage sans contacts d'un type à compensation de la variation de
la tension d'alimentation, pour un moteur à combustion interne, comprenant:
un alternateur (1) destiné à produire un signal de courant alternatif en synchronisme
avec la rotation du moteur;
une bobine d'allumage (3) destinée à produire une tension élevée;
un transistor de puissance (8) destiné à commander par tout ou rien le courant primaire
de la bobine d'allumage;
un transistor d'entrée (4) qui fonctionne sous la dépendance du signal de courant
alternatif; et
un transistor inverseur (5) destiné à commander le transistor de puissance (8), dans
lequel ce transistor inverseur (5) comporte une base connectée à un collecteur du
transistor d'entrée (4), un émetteur connecté à une première borne d'une source d'énergie
(2) par l'intermédiaire d'une résistance d'émetteur commune (21) avec le transistor
d'entrée (4) qui comporte un émetteur également connecté à la première borne de la
source d'énergie (2), par l'intermédiaire de la résistance d'émetteur commune (21),
et le transistor inverseur (5) comporte un collecteur connecté par l'intermédiaire
d'une résistance de collecteur (20) à la seconde borne de la source d'énergie (2);
caractérisé en ce qu'un circuit série formé par une résistance (23) et une diode Zener
(11) est connecté en parallèle avec la résistance de collecteur (20) et entre le collecteur
du transistor inverseur (5) et la seconde borne de la source d'énergie (2), grâce
à quoi une augmentation de la tension d'alimentation de la source d'énergie (2) dépassant
une valeur prédéterminée provoque la conduction de la diode Zener (11) de façon à
faire circuler un courant, lorsque le transistor inverseur (5) est conducteur, de
la source d'énergie (2) vers la résistance d'émetteur commune (21), par l'intermédiaire
de la résistance de collecteur (20), du circuit série (23, 11) et du transistor inverseur
(5) à l'état conducteur, ce qui a pour effet de décaler le niveau de fonctionnement
du transistor d'entrée (4) sous la dépendance de l'augmentation de la tension d'alimentation,
d'une manière telle que le transistor d'entrée (4) se débloque et se bloque à des
niveaux différents du signal de courant alternatif, à cause de l'augmentation et de
la diminution du courant qui circule dans la résistance d'émetteur commune (21), résultant
du dé. blocage et du blocage du transistor inverseur (5).
2. Un système d'allumage sans contacts, selon la revendication 1, caractérisé en ce
que la diode Zener (11) augmente un angle de conduction sur lequel le transistor de
puissance (8) est conduc. teur, lorsque la tension d'alimentation est inférieure à
la valeur prédéterminée, et elle diminue l'angle de conduction lorsque la tension
d'alimentation est supérieure à la valeur prédéterminée.